Re: [PATCH 1/1] drm/xe: Add null pointer check for xe_migrate_copy

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Sep 18, 2024 at 03:10:00PM -0700, Zhanjun Dong wrote:
> Add null pointer check for parameter src.
> Update lack source flag to include resource is null case in xe_bo_move
> before xe_migrate_copy called.
> 
> Signed-off-by: Zhanjun Dong <zhanjun.dong@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_bo.c      |  4 ++--
>  drivers/gpu/drm/xe/xe_migrate.c | 24 ++++++++++++++++--------
>  2 files changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 5f2f1ec46b57..761130f0e9a9 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -682,8 +682,8 @@ static int xe_bo_move(struct ttm_buffer_object *ttm_bo, bool evict,
>  	tt_has_data = ttm && (ttm_tt_is_populated(ttm) ||
>  			      (ttm->page_flags & TTM_TT_FLAG_SWAPPED));
>  
> -	move_lacks_source = handle_system_ccs ? (!bo->ccs_cleared)  :
> -						(!mem_type_is_vram(old_mem_type) && !tt_has_data);
> +	move_lacks_source = !old_mem ? true : (handle_system_ccs ? (!bo->ccs_cleared)  :
> +					       (!mem_type_is_vram(old_mem_type) && !tt_has_data));

I'd write it like this:

old_mem || (conditional)

But I think if old_mem is NULL this condition always evaluates to true.

- old_mem_type will be XE_PL_SYSTEM.
- ttm should be NULL (I think), thus handle_system_ccs should be false
  and tt_has_data should be false

>  
>  	needs_clear = (ttm && ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC) ||
>  		(!ttm && ttm_bo->type == ttm_bo_type_device);
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
> index cfd31ae49cc1..45bba0d731ec 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -774,14 +774,22 @@ struct dma_fence *xe_migrate_copy(struct xe_migrate *m,
>  	u64 src_L0, dst_L0;
>  	int pass = 0;
>  	int err;
> -	bool src_is_pltt = src->mem_type == XE_PL_TT;
> -	bool dst_is_pltt = dst->mem_type == XE_PL_TT;
> -	bool src_is_vram = mem_type_is_vram(src->mem_type);
> -	bool dst_is_vram = mem_type_is_vram(dst->mem_type);
> -	bool copy_ccs = xe_device_has_flat_ccs(xe) &&
> -		xe_bo_needs_ccs_pages(src_bo) && xe_bo_needs_ccs_pages(dst_bo);
> -	bool copy_system_ccs = copy_ccs && (!src_is_vram || !dst_is_vram);
> -	bool use_comp_pat = xe_device_has_flat_ccs(xe) &&
> +	bool src_is_pltt, dst_is_pltt;
> +	bool src_is_vram, dst_is_vram;
> +	bool copy_ccs, copy_system_ccs;
> +	bool use_comp_pat;
> +
> +	if (!src)
> +		return ERR_PTR(-EINVAL);

Can you explain if this function is called with src == NULL? That seems
to be problem in the upper layers if that happens.

Matt

> +
> +	src_is_pltt = src->mem_type == XE_PL_TT;
> +	dst_is_pltt = dst->mem_type == XE_PL_TT;
> +	src_is_vram = mem_type_is_vram(src->mem_type);
> +	dst_is_vram = mem_type_is_vram(dst->mem_type);
> +	copy_ccs = xe_device_has_flat_ccs(xe) && xe_bo_needs_ccs_pages(src_bo) &&
> +		xe_bo_needs_ccs_pages(dst_bo);
> +	copy_system_ccs = copy_ccs && (!src_is_vram || !dst_is_vram);
> +	use_comp_pat = xe_device_has_flat_ccs(xe) &&
>  		GRAPHICS_VER(xe) >= 20 && src_is_vram && !dst_is_vram;
>  
>  	/* Copying CCS between two different BOs is not supported yet. */
> -- 
> 2.34.1
>